News Article
University Of Durham Physicists Have Produced A Magnetic NOT Gate (Science,
The gate consists of a track of magnetic nickel-iron alloy wire. The
magnetisation runs parallel to the track. Small distance changes are created
by a domain wall where one magnetisation meets one in the opposite
direction, either head-to-head or toe-to-toe. These two configurations at
the domain wall are given logic values (0 or 1). Changing the external
magnetic field pushes the domain walls down the track. In a Y-shaped track
that doubles back on itself, however, the orientation of the wall is flipped
as it is pushed round the bend (H-H goes to T-T or T-T goes to H-H),
creating the NOT function. The device operates at room temperature.
The research team put 11 gates in a loop and pushed the domain wall around
the circuit up to 100,000 times without error. "We think we'll have a fully
functioning logic system within a year," Cowburn told Science.
US researchers from two separate teams are claiming single atom and single
molecule transistor effects, both reporting in Nature (June 13).
Scientists from Cornell University and the University of California Berkeley
used cobalt attached to gold electrodes by organic structures ("Coulomb
blockade and the Kondo effect in single-atom transistors"). The electrodes
supplied the source and drain and the doped silicon substrate provided the
back gate. Measurements at 0.1 of a degree above absolute zero (100mK)
showed single-electron transistor behaviour (Coulomb blockade), although
Cornell professor Paul McEuen points out that amplification was not
achieved. The behaviour disappeared in a control without cobalt.
Work with an organic molecule with shorter links to the electrodes
demonstrated conductance near the theoretical limit. A logarithmic
temperature dependence and a magnetic field splitting of the cobalt's
electronic state indicates that the "Kondo effect" is important to the
current flow. The Kondo effect relates to "spin" being important to the flow
of electrons onto and off the cobalt atom. The temperature scale for the
effect is measured by the "Kondo temperature", which is estimated to vary
between 10-25K in these experiments. The values are higher than those
realised on quantum dot or nanotube systems.
The second team - from Harvard and University of California Berkeley -
report experiments on a similar arrangement with two vanadium atoms ("Kondo
resonance in a single-molecule transistor"). A narrow gold bridge
(source-drain) was fabricated on an aluminium pad with an oxide layer (gate)
of the order of 3nm. Here Kondo behaviour was found up to 30K. A Kondo
temperature of more than 30K was found "representing (to our knowledge) the
highest Kondo temperature reported to date for a quantum-dot type system".
Scientists from the Max Planck Institut fuer Mikrostrukturphysik
(Halle/Saale, Germany) have made progress in depositing crystalline
ferroelectric layers on silicon substrates. Such layers are being developed
with non-volatile memory applications in mind. The researchers used pulsed
laser deposition (PLD) of "a axis"-oriented La-subsituted Bi4Ti3O12 (BLT) on
an yttria-stabilised zirconia-buffered silicon substrate using SrRuO3 as a
bottom electrode. The a-axis oriented film can achieve a remanent electric
polarisation of 32microcoulombs/cm2.
The US National Electronics Manufacturing Initiative (NEMI) has set up three
new optoelectronics projects. These will focus on optic adhesives, fibre
handling and fibreoptic signal performance. A separate "special study group"
will investigate the use of optoelectronics in substrates such as PCBs.
magnetisation runs parallel to the track. Small distance changes are created
by a domain wall where one magnetisation meets one in the opposite
direction, either head-to-head or toe-to-toe. These two configurations at
the domain wall are given logic values (0 or 1). Changing the external
magnetic field pushes the domain walls down the track. In a Y-shaped track
that doubles back on itself, however, the orientation of the wall is flipped
as it is pushed round the bend (H-H goes to T-T or T-T goes to H-H),
creating the NOT function. The device operates at room temperature.
The research team put 11 gates in a loop and pushed the domain wall around
the circuit up to 100,000 times without error. "We think we'll have a fully
functioning logic system within a year," Cowburn told Science.
US researchers from two separate teams are claiming single atom and single
molecule transistor effects, both reporting in Nature (June 13).
Scientists from Cornell University and the University of California Berkeley
used cobalt attached to gold electrodes by organic structures ("Coulomb
blockade and the Kondo effect in single-atom transistors"). The electrodes
supplied the source and drain and the doped silicon substrate provided the
back gate. Measurements at 0.1 of a degree above absolute zero (100mK)
showed single-electron transistor behaviour (Coulomb blockade), although
Cornell professor Paul McEuen points out that amplification was not
achieved. The behaviour disappeared in a control without cobalt.
Work with an organic molecule with shorter links to the electrodes
demonstrated conductance near the theoretical limit. A logarithmic
temperature dependence and a magnetic field splitting of the cobalt's
electronic state indicates that the "Kondo effect" is important to the
current flow. The Kondo effect relates to "spin" being important to the flow
of electrons onto and off the cobalt atom. The temperature scale for the
effect is measured by the "Kondo temperature", which is estimated to vary
between 10-25K in these experiments. The values are higher than those
realised on quantum dot or nanotube systems.
The second team - from Harvard and University of California Berkeley -
report experiments on a similar arrangement with two vanadium atoms ("Kondo
resonance in a single-molecule transistor"). A narrow gold bridge
(source-drain) was fabricated on an aluminium pad with an oxide layer (gate)
of the order of 3nm. Here Kondo behaviour was found up to 30K. A Kondo
temperature of more than 30K was found "representing (to our knowledge) the
highest Kondo temperature reported to date for a quantum-dot type system".
Scientists from the Max Planck Institut fuer Mikrostrukturphysik
(Halle/Saale, Germany) have made progress in depositing crystalline
ferroelectric layers on silicon substrates. Such layers are being developed
with non-volatile memory applications in mind. The researchers used pulsed
laser deposition (PLD) of "a axis"-oriented La-subsituted Bi4Ti3O12 (BLT) on
an yttria-stabilised zirconia-buffered silicon substrate using SrRuO3 as a
bottom electrode. The a-axis oriented film can achieve a remanent electric
polarisation of 32microcoulombs/cm2.
The US National Electronics Manufacturing Initiative (NEMI) has set up three
new optoelectronics projects. These will focus on optic adhesives, fibre
handling and fibreoptic signal performance. A separate "special study group"
will investigate the use of optoelectronics in substrates such as PCBs.
